Casting molds having decomposable hollow risers

ABSTRACT

A casting mold in which a pattern is removably positioned in a mold box and a hollow shell is operably related to a portion of the periphery of the pattern for a supplementary feeding space (riser). Molding material within the box surrounds the pattern and hollow shell so that upon the removal of the pattern, the space occupied by the pattern and the hollow shell remain surrounded by molding material, the hollow shell being of a framed plastic material capable of burning or vaporizing at ordinary casting temperatures.

United States Patent name an" Inventor 14/16 Norbertstrme, Cologne, Germany Appl. No. 730,729 Filed May 21, 1968 Continuation-impart of Ser. No. 323,376, Nov. 13,1963, abandoned. Patented Aug. 31, 1971' Priority Nov. 16,1962, Apr. 3, 1963,.luly 8, 1963 Germany P 14 58 135.2, P 14 33 938.9 and P 14 33 940.3 1

CASTING MOLDS HAVING DECOMPOSABLE HOLLOW IUSERS 5 Claims, 4 Drawing Figs. 11.5.1! 164/360, 164/41 1111.61 B224: 9/08 Fleldolseorch 164/360, 359, 246, 34, 41

References Cited UNITED STATES PATENTS 2,491,096 12/1949 Feagin l64/41X FOREIGN PATENTS 1,089,126 9/1960 Gennany 164/360 1,178,977 10/1964 Germany Primer Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel Attorney-Holman & Stern ABSTRACT: A casting mold in which a pattem is removably positioned in a mold box and a hollow shell is operably' related to a portion of the periphery of the-pattem for a supplementary feeding space (riser). Molding material within the box surrounds the pattern and hollow shell so that upon the removal of the pattern, the space occupied by the pattern and the hollow shell remain surrounded by molding material, the hollow shell being of a framed plastio material capable of burning or vaporizing at ordinary casting temperatures.

PATENTEU M831 l97l 3,602,292

FIG]

INVENTOR E. BHUIL ATTORNEY-S CASTING MOLDS HAVING DECOMPOSABLE HOLLOW RISERS This application is a continuation-in-part of application Ser. No. 323,376, filed Nov. 13, 1963, now abandoned.

This invention relates to the production of molds for casting metals and more particularly castings with a blind dead head or riser and in which a hollow body adapted to the intended configuration of the riser having a small and approximately constant wall thickness is affixed at the necessary points of the pattern and surrounded with molding material simultaneously with the pattern and when the pattern is removed, the prefabricated hollow body riser remains in the mold.

More particularly, the hollow body of the present invention is designed in shell form and is composed of a material capable of burning or vaporizing at ordinary casting temperatures and specifically is composed of a foamed plastic.

It is known in the art to employ patterns of expanded plastic and leave such expanded plastic patterns in the mold during the casting operation so that the plastic is vaporized by the heat developed by the liquid metal. However, these expanded plastic patterns are solid bodies and it has been assumed that only solid bodies of expanded plastic can be utilized in order to avoid the explosion hazard by the vaporizing of the plastic by the liquid metal.

- the large inner surface of the hollow body present during the entrance of the melt into such a body and which area would be exposed to the radiant heat of the melt, that a gas pressure would be produced by the sudden vaporization of the hollow body and the melt would be pushed back.

In addition, experiments have demonstrated that hollow e 2 hollow shells,

FIG. 3 is a vertical sectional view through a hollow shell composed of expanded plastic for the formation of a feeder zone, and y FIG. 4 is a view similar to FIG. 3 of a modified type of hollow shell.

As illustrated in FIG. 1, a mold box defined by an upper part 1 and a lower part 2 has a pattern 3, preferably of wood and of the desired configuration, embedded in molding material 4, such as mold'sand. -A feeder zone is constituted by hollow bodies Sand such bodies are in the nature of a shell formed from a foam plastic, particularly polystyrene. A core 6 of gas permeable'material is inserted or fitted into the dome of the hollow shell.

It will be appreciated that after the pattern 3 is removed, the metal is poured into the mold box and each hollow shell 5 will be burned or vaporized by the casting metal.

With reference to FIG. 3, it will be noted that the hollow shell 5 is composed of two shell halves 5a and 5b which are secured together along junction 7. An opening 8 is provided in the dome of the hollow shell for receiving the gas permeable core 6. v

In FIG. 4, there is illustrated a modified type of hollow shell 5 and is provided with a continuous projecting edge 9 which tapers outwardly and which permits the shell 5 to be secured laterally at the pattern as clearly illustrated in FIG. 1.

This invention is not to be confined to any strict conformity to the showings in the drawings but changes or modifications bodies of foam plastic do possess sufficient strength for the purposes involved.

A further advantage of the present invention is that the foam plastic constituting the shell riser is pressed into the molding material surrounding the riser and easily taken up thereby when decomposed by the radiant heat of the melt and the heated air urged ahead of the melt as a result of the small quantity of the plastic. From the above, it results that feeders or risers designed as hollow shells and fabricated of foam plastic permit better casting than those feeders or risers which have not been designed in the form of a shell.

Further objects and advantages of the present invention will be more readily apparent to persons skilled in the art from the following detailed description and annexed drawings and in which drawings:

FIG. 1 is a vertical sectional view taken through a mold box provided with a pattern and attached hollow shells of foam plastic for the formation of a feeder zoneembedded in a molding material, such as sand, v

FIG. 2 is a top plan view of FIG. 1 with the mold sand having been omitted for a clearer representation of the pattern and may be made therein so long as such changes or modifications mark no material departure from the spirit and scope of the appended claims.

1. In a casting mold of the type including a mold box, a pattern removably positioned therein, at least one riser operably related to a portion of the periphery of said pattern for providing a supplementary feeding space, and molding material within the mold box surrounding the pattern and riser so that upon removal of the pattern from the mold box the space occupied by, the pattern and the riser remain in the molding material, the improvement being that said riser is a hollow shell substantially made of foamed plastic material capable of burning or vaporizing at ordinary casting temperatures.

' 2. A casting mold as claimed in claim 1 wherein said hollow shell has a substantially constant wall thickness and said hollow shell comprises two complementary parts secured together. 1

3. In a casting mold of the type'including a mold box, a pattern removably positioned therein, at least one riser operably related to a portion of the periphery of the pattern for providing a supplementary feeding space, and molding material within the box encompassing the pattern and hollow body so that upon the removal of the pattern, the volume occupied by the pattern as well as said riser remain surrounded by the molding material, the improvement being that said riser is a hollow body and consists of two shell halves secured together, said halves each being made substantially of foamed plastic material capable of burning burning vaporizing at the casting temperature of the metal being cast.

4. A casting mold as claimed in claim 1 wherein said foamed plastic is polystyrene. f

5. A casting mold as claimed in claim 1 wherein there is a hole in the top of said' hollow shell which is closed by a gas permeable core. 

1. In a casting mold of the type including a mold box, a pattern removably positioned therein, at least one riser operably related to a portion of the periphery of said pattern for providing a supplementary feeding space, and molding material within the mold box surrounding the pattern and riser so that upon removal of the pattern from the mold box the space occupied by the pattern and the riser remain in the molding material, the improvement being that said riser is a hollow shell substantially made of foamed plastic material capable of burning or vaporizing at ordinary casting temperatures.
 2. A casting mold as claimed in claim 1 wherein said hollow shell has a substantially constant wall thickness and said hollow shell comprises two complementary parts secured together.
 3. In a casting mold of the type including a mold box, a pattern removably positioned therein, at least one riser operably related to a portion of the periphery of the pattern for providing a supplementary feeding space, and molding material within the box encompassing the pattern and hollow body so that upon the removal of the pattern, the volume occupied by the pattern as well as said riser remain surrounded by the molding material, the improvement being that said riser is a hollow body and consists of two shell halves secured together, said halves each being made substantially of foamed plastic material capable of burning burning vaporizing at the casting temperature of the metal being cast.
 4. A casting mold as claimed in claim 1 wherein said foamed plastic is polystyrene.
 5. A casting mold as claimed in claim 1 wherein there is a hole in the top of said hollow shell which is closed by a gas permeable core. 